Several of the professional game engines I have worked on (PS2 in particular) have some of the rain particles exist in 2D screen space. In this way, there is always a layer of camera-relative rain that gives the general impression of rain.
Then, 3D particles fill out the rain, giving it depth and splashes. The result is much finer control over the rain and of course when you move the camera the 2D rain always stays with it filling in the gaps until the new 3D particles arrive to flush it all out.
Ken
Then, 3D particles fill out the rain, giving it depth and splashes. The result is much finer control over the rain and of course when you move the camera the 2D rain always stays with it filling in the gaps until the new 3D particles arrive to flush it all out.
Ken